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Subject: Re: [OMPI users] memalign usage in OpenMPI and it's consequences for TotalVIew
From: Peter Thompson (peter.thompson_at_[hidden])
Date: 2009-10-01 14:25:52


Took a look at the changes and that looks like it should work. It's certainly
not in 1.3.3, but as long as you guys are on top of it, that relieves my
concerns ;-)

Thanks,
PeterT

Samuel K. Gutierrez wrote:
> Ticket created (#2040). I hope it's okay ;-).
>
> --
> Samuel K. Gutierrez
> Los Alamos National Laboratory
>
> On Oct 1, 2009, at 11:58 AM, Jeff Squyres wrote:
>
>> Did that make it over to the v1.3 branch?
>>
>>
>> On Oct 1, 2009, at 1:39 PM, Samuel K. Gutierrez wrote:
>>
>>> Hi,
>>>
>>> I think Jeff has already addressed this problem.
>>>
>>> https://svn.open-mpi.org/trac/ompi/changeset/21744
>>>
>>> --
>>> Samuel K. Gutierrez
>>> Los Alamos National Laboratory
>>>
>>> On Oct 1, 2009, at 11:25 AM, Peter Thompson wrote:
>>>
>>> > We had a question from a user who had turned on memory debugging in
>>> > TotalView and experience a memory event error Invalid memory
>>> > alignment request. Having a 1.3.3 build of OpenMPI handy, I tested
>>> > it and sure enough, saw the error. I traced it down to, surprise, a
>>> > call to memalign. I find there are a few places where memalign is
>>> > called, but the one I think I was dealing with was from malloc.c in
>>> > ompi/mca//io/romio/romio/adio/common in the following lines:
>>> >
>>> >
>>> > #ifdef ROMIO_XFS
>>> > new = (void *) memalign(XFS_MEMALIGN, size);
>>> > #else
>>> > new = (void *) malloc(size);
>>> > #endif
>>> >
>>> > I searched, but couldn't find a value for XFS_MEMALIGN, so maybe it
>>> > was from opal_pt_malloc2_component.c instead, where the call is
>>> >
>>> > p = memalign(1, 1024 * 1024);
>>> >
>>> > There are only 10 to 12 references to memalign in the code that I
>>> > can see, so it shouldn't be too hard to find. What I can tell you
>>> > is that the value that TotalView saw for alignment, the first arg,
>>> > was 1, and the second, the size, was 0x100000, which is probably
>>> > right for 1024 squared.
>>> >
>>> > The man page for memalign says that the first argument is the
>>> > alignment that the allocated memory use, and it must be a power of
>>> > two. The second is the length you want allocated. One could argue
>>> > that 1 is a power of two, but it seems a bit specious to me, and
>>> > TotalView's memory debugger certainly objects to it. Can anyone tell
>>> > me what the intent here is, and whether the memalign alignment
>>> > argument is thought to be valid? Or is this a bug (that might not
>>> > affect anyone other than TotalView memory debug users?)
>>> >
>>> > Thanks,
>>> > Peter Thompson
>>> > _______________________________________________
>>> > users mailing list
>>> > users_at_[hidden]
>>> > http://www.open-mpi.org/mailman/listinfo.cgi/users
>>>
>>> _______________________________________________
>>> users mailing list
>>> users_at_[hidden]
>>> http://www.open-mpi.org/mailman/listinfo.cgi/users
>>>
>>
>>
>> --
>> Jeff Squyres
>> jsquyres_at_[hidden]
>>
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